This invention relates generally to a suction pipe apparatus for an internal-combustion engine and, more particularly, to a suction pipe apparatus for an internal-combustion engine which is provided with a fuel injection system for intermittently injecting fuel into the intake pipes connected to the engine cylinder head.
In an internal-combustion engine, one of the components having one of the highest levels of structure-borne noise (i.e., noise transmitted through and by the structural components of the engine) is the cylinder head. The cylinder head is subjected to noise vibrations produced by combustion and by operation of the intake air control apparatus. If transmitted to the suction or intake pipes, these high structure-borne noise levels can result in production of considerable levels of reflected noise, due to the relatively large surface area of the intake pipes. In the case of engines with intermittent fuel injection, high frequency pulse-like ticking sounds are superimposed on these noises at low speeds. The ticking sounds are reflected, in part, by the cylinder head, the suction pipes and the fuel collector pipe, and, in part, directly by the surface of the fuel injection valves. With each reduction in the levels of engine noises from other sources, these ticking sounds become more noticable and disturbing.
German Unexamined Published Application (DE-OS) No. 28 24 205 and German Examined Published Application (DE-AS) No. 11 56 276 show the use of elastic flange elements to connect the intake pipes to the cylinder head. The purpose of these elements is to de-couple the cylinder head vibrations from the intake pipes, thus provided a degree of insulation with respect to structure-borne noises. However, in these cases, the elastic flange element shown does not provide for a durable connection of the intake pipe to the cylinder head, and measures for reducing the ticking noises produced by the fuel injection valves are not provided.
It is an objective of this invention to provide a suction pipe apparatus for an internal-combustion engine of the above-noted type which includes a durable, secure and highly stable structure for fastening the suction pipe to the cylinder head and which, in addition, provides for a reduction in the noise produced by the fuel injection valves.
This objective is attained in a suction pipe apparatus which comprises a structure-borne-noise-insulating connecting pipe arranged between the cylinder head and the intake pipe. The connecting pipe is provided with a sleeve-like portion for receiving a fuel injection valve. The inner surface of the sleeve-like portion conforms to the shape of the fuel injection valve, allowing the portion to tightly enclose the outer, noise-reflecting surface of the valve. The connecting pipe and sleeve-shaped portion are formed from an elastomer, such as a thermoplastic material. In a preferred embodiment, the connecting pipe and the sleeve-shaped portion are integrally formed to provide a unitary structure. In an especially preferred embodiment, a flange portion of the connecting pipe is provided with a stiffening member to enhance the strength and durability of the suction pipe/cylinder head connection. The elastomeric connecting pipe may be clamped to the intake pipe or, in an alternative and advantageous embodiment, integrally formed onto the intake pipe by known techniques of injection molding.
The primary advantage achieved by means of this invention is a reduction in the level of engine noise emissions. The suction pipe apparatus of the present invention provides effective insulation of the suction pipes from the cylinder head, with respect to structure-borne noise, reducing the level of subsequently reflected sounds. In addition, the pipe apparatus provides for the structure-borne-noise-insulating and encapsulating of the fuel injection valves. Consequently, high-frequency pulse-like ticking noises are prevented. The encapsulating enclosure provides for absorption of airborne noise and insulation of the fuel injectors and suction pipes from structure-borne noises of the cylinder head. The elastomer sleeve which tightly encloses the fuel injectors also provides for damping of structure-borne noises.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawing which show, for purposes of illustration only, embodiments in accordance with the present invention.